Double-bed circular knitting machine with device for correcting automatically variations of the distance between the needle cylinder and the dial

ABSTRACT

A double-bed circular knitting machine with device for correcting automatically variations of the distance between the needle cylinder and the dial, comprising a supporting structure which supports, so that it can rotate about its own vertically oriented axis, a needle cylinder and a dial, which is arranged above and coaxially to the needle cylinder. Elements are provided for feeding threads to the needles, the machine comprising a device for correcting automatically the variations of the distance between the needle cylinder and the dial.

The present invention relates to a double-bed circular knitting machine with device for correcting automatically variations of the distance between the needle cylinder and the dial.

As is known, double-bed circular knitting machines comprise a supporting structure that has a base for resting on the ground and supports, so that it can rotate about its own axis, which is oriented vertically, a needle cylinder and a dial that is arranged above and coaxially to the needle cylinder.

On the lateral surface of the needle cylinder a plurality of axial slots is defined, each accommodating a needle that can slide on command with alternating motion along the corresponding axial slot in order to engage the thread or threads fed to the needles, at a feed or drop of the machine, and form knitting.

In the dial a plurality of radial slots is defined, each of which in turn accommodates a needle that can slide with alternating motion along the corresponding radial slot in order to engage the thread or threads fed to the needles, at a feed or drop of the machine, and form knitting.

The actuation of the needles with alternating motion along the slot in which they are accommodated is performed by means of the direct coupling of a heel of the needles with paths defined by cams that are connected to the supporting structure of the machine and face respectively the external lateral surface of the needle cylinder and the upper face of the dial, or indirectly by means of elements for actuating the needles that engage the cams and are connected to the needles.

By means of the combined actuation of the needles arranged in the cylinder and of the needles arranged in the dial, it is also possible to perform the passage of the stitches of knitting from the needles of the cylinder to the needles of the dial or vice versa.

In these machines, the minimum distance between the beds, i.e., between the needle cylinder and the dial in the point of knitting formation, is a characteristic datum of the machine, which during the construction of the machine is adjusted with precision by the manufacturer, according to the gauge of the machine.

This distance, termed in the jargon “loop gap”, can be modified manually by the user by means of an adapted device that can be controlled manually in order to obtain the desired type of knitting.

During the operation of the machine, in order to avoid evident defects on the produced knitting, the value of the loop gap must remain unchanged. This aspect is even more important in circular knitting machines that produce a continuous sheet, because a variation of the characteristics of the knitting within a same sheet is not tolerable.

This requirement, however, is difficult to meet precisely, because during the operation of the machine, due to the sliding of the needles inside the needle cylinder and the dial and because of the sliding of the needles against the cams that actuate them, the temperature of the components of the beds increases considerably. Indicatively, the thermal gradient during the operation of a double-bed machine is approximately 40° C., starting from ambient temperature.

The temperature variation generates a deformation of all the components of the beds that is not regular and uniform for each component, and this fact is the main cause of the unwanted variation of the loop gap value during the operation of the machine.

In some types of double-bed knitting machine, especially in high-gauge machines, indicatively with a gauge (number of needles per inch) equal to 50, the loop gap value must be very small, indicatively 0.8 mm, and the slightest variation of the loop gap value causes a change in the weight of the manufactured knitting that makes the knitting unusable.

This problem arises from the fact that the variation of the loop gap value generates an increase or a decrease in the tension of the threads during their feeding to the machine. As is known, in fact, the threads are supplied to the machine by adapted feeders that supply an always-constant quantity of thread. In order to obtain good quality knitting, the tension with which the threads are supplied to the machine must remain always constant. Therefore, when the loop gap value increases and the quantity of thread supplied remains constant, there is an increase in the tension of the threads that causes a variation of the weight and appearance of the manufactured knitting.

If, because of the shape of the bed components, the loop gap value increases as the temperature decreases, it may occur that when the knitting machine is left still or off for a few hours after having worked regularly, the temperature of the beds can drop to ambient temperature, causing an increase of the loop gap value of a few tenths of a millimeter. If the knitting machine is started and one begins to produce knitting without any remedy, the threads fed to the machine would break because they would be subjected to an excessive tension.

In order to avoid this danger, the user corrects manually the tension of the threads by adjusting the feeding devices so as to be able to start the machine and then perform continuous adjustments of the tension of the threads until the operating temperature stabilizes.

This solution, however, requires continuous monitoring and a large number of interventions on the machine by an operator and entails in any case the discarding of the produced knitting until the operating temperature is reached.

Some manufacturers have tried to solve this problem by inserting elastic elements in the dial so as to compensate for the thermal deformations or by equipping the machines with a heating system that brings the beds to the operating temperature before starting.

These solutions, however, are unable to solve in a fully satisfactory manner the problem of the variation of the loop gap value as a consequence of the variation of the temperature of the beds during the operation of these machines.

The aim of the present invention is to solve the above mentioned problem, by providing a double-bed circular knitting machine with a device for correcting automatically variations of the distance between the two beds, or loop gap, caused by the temperature variations of the beds during the operation of the knitting machine, i.e., to adapt the distance or loop gap between the two beds to the supply tension of the threads supplied to the needles of the machine.

Within this aim, an object of the invention is to provide a machine provided with a device that avoids constant monitoring of the machine by the operator and reduces the manual interventions of the operator in the transitional period of starting the machine until the operating temperature is reached.

Another object of the invention is to provide a machine with a device capable of ensuring high precision in the adjustment of the distance between the two beds or loop gap.

A further object of the invention is to provide a machine with a device that offers the greatest assurances of safety and reliability in use.

Another object of the invention is to provide a machine with a device that does not preclude the possibility of manual intervention on the machine in order to vary the distance between the two beds to perform adjustment or maintenance interventions.

This aim and these and other objects that will become better apparent hereinafter are achieved by a double-bed circular knitting machine with device for correcting automatically variations of the distance between the needle cylinder and dial, comprising a supporting structure which supports, so that it can rotate about its own vertically oriented axis, a needle cylinder and a dial which is arranged above and coaxially to said needle cylinder, said needle cylinder having, on its lateral surface, a plurality of axial slots, each of which accommodates slidingly a needle that can be actuated with an alternating motion along the corresponding axial slot to form knitting and said dial having a plurality of radial slots, each of which accommodates slidingly a needle that can be actuated with alternating motion along the corresponding radial slot to form knitting, means being provided for feeding threads to said needles, characterized in that it comprises a device for correcting automatically the variations of the distance between the needle cylinder and the dial, comprising:

means for detecting the tension of n threads fed to the needles of the machine to form knitting;

movement means, which are connected to said dial and can be actuated to actuate the movement of said dial along its axis with respect to said needle cylinder;

an actuation and control element of the electronic type, which is functionally connected to said tension detection means and is adapted to actuate said movement means in relation to the tension of the threads detected by said tension detection means.

Further characteristics and advantages of the invention will become better apparent from the description of a preferred but not exclusive embodiment of the machine according to the invention, illustrated by way of non-limiting example in the accompanying drawings, wherein:

FIG. 1 is a schematic view of a portion of the machine according to the invention, related to the needle cylinder and to the dial, shown in partial cross-section along a plane that passes through the axis of the needle cylinder and the dial;

FIG. 2 is an enlarged-scale view of a detail of FIG. 1;

FIG. 3 is an enlarged-scale view of another detail of FIG. 1;

FIG. 4 is an enlarged-scale view of a further detail of FIG. 1;

FIG. 5 is a schematic sectional view of FIG. 1, taken along the line V-V.

With reference to the figures, the machine according to the invention, generally designated by the reference numeral 1 and illustrated only partially for the sake of simplicity, comprises, in a per se known manner, a supporting structure 2 which supports, so that it can rotate about its own vertically oriented axis 3, a needle cylinder 4 and a dial 5 which is arranged above and coaxially to the needle cylinder 4.

The needle cylinder 4 has, on its lateral surface, a plurality of axial slots 6, each of which accommodates slidingly a needle 7 that can be actuated with an alternating motion along the corresponding axial slot 6 to form knitting. The actuation of the needles 7 arranged in the needle cylinder 4 is actuated by means of corresponding actuation cams 8 that face the lateral surface of the needle cylinder 4 and are connected to supporting elements 9 which are integral with the supporting structure 2 of the machine as regards the rotary motion about the axis 3 of the needle cylinder 4.

The dial 5 has a plurality of radial slots 10, each of which accommodates a needle 11 that can be actuated with alternating motion along the corresponding radial slot 10 in order to form knitting. The actuation of the needles 11 arranged in the dial 5 is actuated by means of corresponding actuation cams 12 that face in an upward region the needles 11 and are connected to supporting elements 13 which are integral with the supporting structure 2 of the machine as regards the rotary motion of the dial 5, together with the needle cylinder 4, about the common axis 3, with respect to the supporting structure 2 of the machine.

Essentially, the needle cylinder 4 and the dial 5 can rotate about the common axis 3 with respect to the supporting structure 2 and the actuation cams 8, 12, which are connected to the supporting structure 2 of the machine.

The machine is provided, again in a per se known manner, with means 14 for feeding threads 15 to the needles 7 arranged in the needle cylinder 4 and to the needles 11 arranged in the dial 5 in order to allow the needles 7, 11 to form knitting. The means 14 for feeding the threads 15 are constituted by per se known pulleys and guiding elements that define, for the threads 15, a path that runs from the corresponding spool to the needles 7, 11.

According to the invention, the machine comprises a device 16 for correcting automatically the variations of the distance between the needle cylinder 4 and the dial 5. The device 16 comprises: means 17 for detecting the tension of a preset number n of threads 15 fed to the needles 7, 11 of the machine in order to form knitting, movement means 18, which are connected to the dial 5 and can be actuated to actuate the movement of the dial 5 along its axis 3 with respect to the needle cylinder 4, and an actuation and control element 19 of the electronic type, which is connected functionally to the tension detection means 17 and is adapted to actuate the movement means 18 in relation to the tension of the threads 15 detected by the tension detection means 17.

More precisely, the dial 5 is preferably supported, so that it can rotate about its own axis 3, by a central supporting element 20 that extends around the axis 3 of the dial 5 and rests on a substantially disk-shaped fixed supporting element 21, which is integral with the supporting structure 2 of the machine. The fixed supporting element 21 is extended around the central supporting element 20 and has, at the axis 3 of the needle cylinder 4 and of of the dial 5, a hole 23 that is crossed coaxially by the central supporting element 20. The movement means 18 are interposed between the fixed supporting element 21 and the central supporting element 20.

In greater detail, the fixed supporting element 21 has, proximate to the rim of the hole 23 that is crossed by the central supporting element 20, a supporting ring 24 which is extended coaxially to the dial 5 and defines, with its upper face, a supporting surface that is substantially perpendicular to the axis 3 of the dial 5.

The central supporting element 20 has a flange 25, one face of which is substantially at right angles to the axis 3 of the dial 5 and faces in an upper region the supporting surface defined by the supporting ring 24.

The movement means 18 comprise bushes 26 which are accommodated in the supporting ring 24 and are oriented so that their axis is parallel to the axis 3 of the dial 5. The bushes 26 are coupled, by means of a coupling of the screw-and-nut type 27, to pivots 28 which are arranged so that their axes are parallel to the axis 3 of the dial 5 and are fixed to the central supporting element 20.

Each bush 26, in fact, is crossed axially by a threaded hole 29 with which an externally threaded sleeve 30 mates. The sleeve 30 is fixed integrally around the pivot 28, which in turn is rigidly fixed to the flange 25 of the central supporting element 20.

The bushes 26 are regularly mutually spaced around the axis 3 of the dial 5 and have a portion provided as a gear 31 which meshes with a same ring gear 32 which is arranged coaxially to the dial 5 and is accommodated so that it can rotate about its own axis, which coincides with the axis 3, in the supporting ring 24.

The movement means 18 comprise a gearmotor 33, the output shaft of which is connected to a pinion 34 that meshes with the ring gear 32 and can be actuated to cause, by means of the connection established by the ring gear 32, the simultaneous rotation of the gears 31, i.e., of the bushes 26 about the corresponding axes.

The means 17 for detecting the tension of n threads 15 comprise per se known load cells 35, which are arranged along the path of the corresponding thread 15 to be monitored. The number n of the threads 15 to be monitored may vary according to requirement and the degree of precision that one wishes to obtain in monitoring the tension of the threads 15 fed to the machine.

Conveniently, the central supporting element 20 comprises an external element 36, which is cup-shaped and provided with the flange 25 that faces the supporting ring 24, and an internal element 37, shaped like a hollow cylinder, which is arranged inside the external element 36. The internal element 37 and the external element 36 are coaxial to the dial 5 and the internal element 37 supports, so that it can rotate about its own axis 3, a main shaft 38, by means of a pair of bearings 39. The main shaft 38 is connected coaxially, at its lower end, to the dial 5. The internal element 37 and the external element 36 are prevented from rotating about their own axis 3 with respect to the supporting structure 2. Essentially, the internal element 37, during the operation of the machine, cannot rotate with respect to the external element 36 about its own axis, which coincides with the axis 3 of the dial 5 and of the needle cylinder 4, because of the presence of a block 40 that is fixed to a portion of the lateral surface of the internal element 37 and engages, so that it can slide, an axial slot 41 that passes through a portion of the lateral surface of the external element 36. Moreover, the existing coupling between the pivots 28 and the bushes 26, accommodated in adapted seats 42 defined in the supporting ring 24 of the fixed supporting element 21, prevents the rotation of the external element 36 with respect to the supporting structure 2 about the same axis 3.

The internal element 37 is coupled, so that it can slide parallel to the axis 3, to the external element 36 and the relative sliding of these two elements is allowed by the sliding coupling of the block 40 inside the axial slot 41.

Advantageously, the machine comprises means 43 for manually adjusting the position in terms of height of the dial 5 with respect to the needle cylinder 4. The manual adjustment means 43 comprise an actuation ring 44, which is arranged coaxially around the internal element 37 and rests on the upper end of the external element 36, with the interposition of balls 45 so as to be able to rotate about the axis 3 with respect to the external element 36.

The actuation ring 44 is connected, by means of a coupling of the screw-and-nut type 46, to the internal element 37. More precisely, the actuation ring 44 is crossed axially by a threaded hole 47 that mates with a threaded portion 48 of the external lateral surface of the internal element 37 arranged at the upper end of the internal element 37 that protrudes from the upper end of the external element 36.

The actuation ring 44 is manually rotatable to lift or lower the internal element 37, and therefore the dial 5, with respect to the external element 36 and therefore with respect to the needle cylinder 4.

The actuation ring 44 is connected, by means of a chain or belt-type connection 49, to an actuation shaft 50, which is oriented so that its axis is parallel to the axis 3 of the dial 5 and is supported, so that it can rotate about its own axis, by the external element 36. A crank can be connected to the actuation shaft 50 to actuate the manual rotation of the actuation shaft 50, and therefore cause the rotation of the actuation ring 44, in order to perform adjustment or maintenance interventions on the dial 5 when the machine is stopped.

Conveniently, means 51 are provided for detecting the axial movement of the internal element 37 with respect to the external element 36. The means 51 for detecting axial movement, as shown, can be constituted by a sensor, of a known type, which is fixed to the external element 36 internally to the axial slot 41 and detects the position of the block 40, which is integral with the internal element 37.

Moreover, the machine is provided with means 52 for detecting the temperature of the dial 5, and the temperature detection means 52 are functionally connected to the actuation and control element 19, in which movement values of the dial 5 with respect to the needle cylinder 4, obtained empirically during the setting of the machine and correlated to temperature values of the dial 5, are preset, so that the actuation and control element 19 can actuate the movement of the dial 5 with respect to the needle cylinder 4 in relation to the temperature of the dial 5 detected during the starting of the machine.

For the sake of completeness in description, it must be said that the upper end of the main shaft 38 is fixed coaxially to a pinion 53, which can be connected to means for actuating the dial 5 with a rotary motion about its own axis.

Operation of the machine, as regards the device 16 for correcting automatically the variations of the distance between the needle cylinder 4 and the dial 5, is as follows.

The tension of n threads 15 that are fed to the needles 7, 11 of the machine is detected constantly by means of the load cells 35, which transmit the detected values to the actuation and control element 19.

When, due to the variation of the distance between the needle cylinder 4 and the dial 5 at the knitting forming region or loop gap, the tension of the monitored threads 15 undergoes a variation with respect to the value that corresponds to the value of the typical loop gap of the machine, the actuation and control element 19 actuates the gearmotor 33 so that the gearmotor 33 causes, by means of the pinion 34 and the ring gear 32, the rotation of the bushes 26 and, by means of the screw-and-nut coupling 27 that exists between these and the pivots 28, the lifting or lowering of the dial 5 with respect to the needle cylinder 4 so as to bring the loop gap value back to the correct value and therefore return the tension of the threads 15 that feed the machine to the desired value.

In this manner, the tension of the threads 15 that feed the machine remains substantially constant and the quality of the produced knitting is fully satisfactory.

After each stop or switch-off of the knitting machine, since the value of the tension of the threads 15 supplied by the load cells 35 is not fully reliable because the threads 15 undergo relaxation, the temperature of the dial 5 is monitored by way of the temperature detecting means 52, which transmit the detected temperature value to the actuation and control element 19, which on the basis of such temperature value, performs, by means of the actuation of the gearmotor 33, an approximate adjustment of the position of the dial 5 with respect to the needle cylinder 4 according to preset values, which are obtained by empirical tests performed with different temperatures of the dial 5 detected during the setup of the machine. This approximate adjustment is substituted by a more precise adjustment following the correct detection of the tension of the threads 15 performed by the load cells 35, which is indicatively reliable after one or two rotations of the needle cylinder 4 and of the dial 5.

In practice it has been found that the machine with the device for correcting automatically variations of the distance between the needle cylinder and the dial according to the invention fully achieves the intended aim because it makes it possible to maintain constant, with high precision, the value of the tension of the threads that feed the machine, i.e., to keep constant the value of the loop gap, making it possible to produce knitting of constant weight and without defects.

The machine with the device for correcting automatically variations of the distance between the needle cylinder and the dial thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. All the details may further be replaced with other technically equivalent elements.

In practice, the materials used, as well as the dimensions, may be any according to requirements and to the state of the art.

The disclosures in Italian Patent Application No. MI2011A001657 from which this application claims priority are incorporated herein by reference. 

1-11. (canceled)
 12. A double-bed circular knitting machine with device for correcting automatically variations of the distance between the needle cylinder and the dial, comprising a supporting structure which supports, so that it can rotate about its own vertically oriented axis, a needle cylinder and a dial which is arranged above and coaxially to said needle cylinder, said needle cylinder having, on its lateral surface, a plurality of axial slots, each of which accommodates slidingly a needle that can be actuated with an alternating motion along the corresponding axial slot to form knitting and said dial having a plurality of radial slots, each of which accommodates slidingly a needle that can be actuated with alternating motion along the corresponding radial slot to form knitting, means being provided for feeding threads to said needles, further comprising a device for correcting automatically the variations of the distance between the needle cylinder and the dial, comprising: means for detecting the tension of n threads fed to the needles of the machine to form knitting; movement means, which are connected to said dial and can be actuated to actuate the movement of said dial along its axis with respect to said needle cylinder; an actuation and control element of the electronic type, which is functionally connected to said tension detection means and is adapted to actuate said movement means as a function of the tension of the threads detected by said tension detection means.
 13. The machine according to claim 12, wherein said dial is supported, so that it can rotate about its own axis, by a central supporting element which lies around the axis of said dial and rests on a fixed supporting element which is integral with the supporting structure of the machine and is extended around said central supporting element; said movement means being interposed between said fixed supporting element and said central supporting element.
 14. The machine according to claim 13, wherein said fixed supporting element has a supporting ring which is extended coaxially to said dial and defines a supporting surface that is substantially perpendicular to the axis of said dial; said central supporting element having a flange in which one face is substantially perpendicular to the axis of said dial and faces said supporting surface in an upper region; said movement means comprising bushes which are accommodated in said supporting ring and are oriented so that their axis is parallel to the axis of said dial; said bushes being coupled, by means of a coupling of the screw-and-nut type, to pivots which are arranged so that their axes are parallel to the axis of said dial and are fixed to said central supporting element.
 15. The machine according to claim 14, wherein said bushes are mutually evenly spaced around the axis of said dial and have a portion that is provided as a gear, which meshes with a same ring gear which is arranged coaxially to said dial and is accommodated so that it can rotate about its own axis in said supporting ring; said movement means comprising a gearmotor, which is connected to a pinion that meshes with said ring gear and can be actuated for the simultaneous rotation of said bushes.
 16. The machine according to claim 12, wherein said means for detecting the tension of n threads comprise load cells which are arranged along the path of a corresponding thread to be controlled.
 17. The machine according to claim 14, wherein said central supporting element comprises an external element which is provided with said flange that faces said supporting ring and an internal element which is arranged inside said external element; said internal element and said external element being coaxial to said dial and said internal element supporting, so that it can rotate about its own axis, a main shaft which is connected coaxially, by means of its lower end, to said dial; said internal element and said external element being prevented from rotating about their own axis with respect to said supporting structure; said internal element being movable with respect to said external element along the axis of said dial.
 18. The machine according to claim 17, wherein it comprises means for manually adjusting the distance of said dial from said needle cylinder along the common axis, said manual adjustment means comprising: an actuation ring, which is arranged coaxially around said internal element and rests on the upper end of said external element, said actuation ring mating, by means of a coupling of the screw-and-nut type, with said internal element and being manually rotatable to lift or lower said internal element with respect to said external element.
 19. The machine according to claim 18, wherein said actuation ring is connected, by means of a chain or belt-type connection, to an actuation shaft, which is oriented so that its axis is parallel to the axis of said dial and is supported so that it can rotate about its own axis by said external element.
 20. The machine according to claim 17, further comprising means for detecting the axial movement of said internal element with respect to said external element.
 21. The machine according to claim 12, further comprising means for detecting the temperature of the dial, which are functionally connected to said actuation and control element.
 22. The machine according to claim 12, wherein values of the movement of said dial with respect to said needle cylinder, correlated to preset temperature values of the dial, are preset in said actuation and control element in order to actuate, by means of said actuation and control element, the movement of said dial with respect to said needle cylinder as a function of the temperature of the dial detected during machine startup. 